The present invention relates to an IC tag-bearing wiring board provided with a radio IC tag capable of transmitting in-formation recorded in an IC chip by radio and a method of fabricating the IC tag-bearing wiring board.
Radio IC tags are used widely for the identification of articles. A plurality of printed wiring boards included in an electronic apparatus are provided with radio IC tags, respectively, to recognize information about the printed wiring boards. When the electronic apparatus malfunctions and the printed wiring board of the electronic apparatus needs to be changed, pieces of information about the manufacture of the printed wiring board and pieces of technical information about the printed wiring board are read in a noncontact read mode (by radio) from the radio IC tag incorporated into the printed wiring board to collect information characteristic of the printed wiring board to be changed for the support of changing work. Such a radio IC tag has a small IC chip recording information and an antenna for transmitting radio waves representing the information recorded in the IC chip. The IC chip and the antenna are mounted on a first or a second major surface of a printed wiring board to form an IC tag-bearing wiring board.
FIGS. 10(a) and 10(b) are a front perspective view and a top view, respectively, of a conventional IC tag-bearing wiring board. As shown in FIGS. 10(a) and 10(b), an antenna 23 is formed on a part, near the front side surface, of a first major surface (mounting surface) 1a of a printed wiring board 21 and is connected electrically to an IC chip 24 placed on the first major surface 1a of the printed wiring board 21 to form a radio IC tag 22. The radio IC tag 22, similarly to other electronic parts, can be formed by connecting the antenna 23 formed on a second major surface (pattern forming surface) of the printed wiring board 21 to the IC chip 24 placed on the first major surface 1a by through holes. When the IC tag-bearing wiring board thus formed is incorporated into an electronic apparatus, information recorded in the IC chip 24 can be read in a non-contacting read mode by placing a reader, not shown, near the radio IC tag 22 placed near the front side surface of the printed wiring board 21.
A technique is disclosed in, for example, JP Heisei 11-515094 (U.S. Pat. No. 5,995,006, incorporated herein by reference for all purposes) for forming a radio IC tag. The reference describes forming antenna patterns on layers of a multilayer printed wiring board excluding a top layer, mounting an IC chip on a first major surface of the multilayer printed wiring board, and connecting the IC chip to the antenna patterns by, for example, through holes. This technique that forms the antenna patterns in the inner layers is able to use a part mounting space on the first major surface effectively, and the antenna patterns having a short length and formed on the layers are able to form an antenna of a desired length. Thus, the radio IC tag including the antenna can be formed in a small size.
The antenna 23 of the radio IC tag 22 of the conventional IC tag-bearing wiring board shown in FIGS. 10(a) and 10(b) is formed on a part of a first or a second major surface of the printed wiring board 21. The part in which the antenna 13 is formed cannot be used for mounting electronic parts. Although the technique previously disclosed in JP Heisei 11-515094 forms antenna patterns in parts of the inner layers of the multilayer printed wiring board, electronic parts cannot be mounted in a part of the top layer corresponding to the parts of the inner layers in which the antenna patterns are formed. Thus the antenna of the radio IC tag formed on the first or the second major surface of the printed wiring board reduces electronic part packaging efficiency. If the antenna is a dipole antenna, the antenna functions at the highest radiation efficiency when the length of the antenna is equal to λ/2, where λ is the wavelength of radio waves to be transmitted. A printed wiring board having a large surface area must be used to maintain desired communication ability by forming the antenna in a necessary length. The conventional IC tag-bearing wiring board is unable to meet contradictory conditions respectively requiring maintaining a desired communication ability and improving electronic part packaging efficiency.
The conventional IC tag-bearing wiring board is provided with the antenna on the first or the second major surface of the printed wiring board. When the printed wiring board is a multilayer printed wiring board, the antenna is formed on the inner layers of the printed wiring board. Therefore, the antenna of the radio IC tag cannot be formed such that the antenna has a directivity in a desired specific direction. Consequently, radio waves radiated by the antenna of one IC tag-bearing wiring board propagate in a comparatively wide area at a short range. In an electronic apparatus provided with a plurality of stacked IC tag-bearing wiring boards, radio waves radiated by the antennas of the stacked IC tag-bearing wiring boards interfere with each other, and, in some cases, information provided by a desired one of those IC tag-bearing wiring boards cannot be identified.